Urine flow is an important indicator for the dynamic equilibrium of body fluid and functions of heart and kidney. Accurate monitoring of urine flow can assist in judging the development of diseases and in making a treatment plan. Monitoring urine flow is one of the important measures to examine the patient. For critically ill patients, urine flow can often predict kidney disorder before the blood creatinine elevates. Although clinical monitoring of urine flow is an important test which can timely reveal the human body's effective blood circulation and the kidney function, the accuracy and timeliness of the test are by far insufficient; even less attention has been paid to safe and automatic monitoring of urine. Currently, the urine tests for critically ill patients are performed manually and intermittently. This not only increases the workload of the nurses and results in unnecessary costs, but also increases the risk of urine contamination. Furthermore, it may cause delay and mistake in clinical judgments and serious errors.
Also, urine density reflects the concentration function of kidney. A high urine density may relate to dehydration, albuminuria, saccharorrhea, acute nephritis, and high fever etc. A low urine density may indicate problems with kidney concentration function, such as chronic renal glomerulus nephritis, acute nephritis polyuria time, and uremia polyuria time etc. Urine density monitoring is usually performed by intermittently manual sampling and then testing the samples by an instrument. Because of the time gap between the sampling and the testing, urine samples which are not tested quickly may produce precipitations, which result in testing results errors.